US20080142367A1 - In situ plating and etching of materials covered with a surface film - Google Patents

Abstract

Systems and methods for plating and/or etching of hard-to-plate metals are provided. The systems and methods are designed to overcome the deleterious effect of superficial coating or oxide layers that interfere with the plating or etching of certain metal substrates. The systems and methods involve in situ removal of coating materials from the surfaces of the metal substrates while the substrates are either submerged in plating or etching solutions, or are positioned in a proximate enclosure just prior to submersion in the plating or etching solutions. Further, the substrates can be in contact with a suitable patterning mask to obtain patterned oxide-free regions for plating or etching. This in situ removal of coating layers may be achieved by pulse heating or photoablation of the substrate and the inhibiting coating layers. Electrical energy or laser light energy may be used for this purpose. Additionally or alternatively, the coating materials may be removed by mechanical means.

Description

CROSS REFERENCE TO RELATED APPLICATIONS
• This application is a continuation of PCT International Application No. PCT/US06/04329 filed Feb. 8, 2006 based on U.S. provisional patent application Nos. 60/650,870 filed Feb. 8, 2005; 60/675,114 filed Apr. 25, 2005 and 60/700,877 filed Aug. 3, 2005, all of which applications are incorporated by reference in their entireties herein. Further, this application claims the benefit of U.S. provisional patent application Nos 60/815,790 filed Jun. 22, 2006 and 60/845,586 filed Sep. 19, 2006 both of which applications are also incorporated by reference in their entireties herein.
BACKGROUND OF THE INVENTION
• The present invention relates to systems and methods for metal plating and etching of substrates. More particularly, the invention relates to metal plating and etching of readily oxidizable substrates or other substrates with thin layers that inhibit plating and etching.
• Metal plating of articles or base substrates is a common industrial practice. A metal layer may be coated or plated on the surface of an article, for example, for decoration, reflection of light, protection against corrosion, or increased wearing quality. Articles or base substrates, which are made of metal or non-metallic material, may be plated with suitable coating metals using techniques such as electroplating, electroless plating, metal spraying, hot dip galvanizing, vacuum metallization or other available processes. Plating by electrolysis, or electroplating, is a commonly used technique for metal plating because it permits the control of the thickness of the plating. Cadmium, zinc, silver, gold, tin, copper, nickel, and chromium are commonly used plating/coating metals. In immersion or electroless plating, some metals are directly precipitated, without electricity, from chemical solutions onto the surface of the substrates. The silvering of mirrors is a type of plating in which silver is precipitated chemically on glass. Any of the common metals and some nonmetals, e.g., plastics, with suitably prepared (e.g., etched) surfaces can be used as the article or base substrate material.
• However, some metals (e.g., aluminum and refractory metals like tungsten, tantalum and molybdenum), which have desirable physical or structural properties for use as base substrate material, are extremely difficult to plate by simple immersion plating or electroplating techniques. The difficulty in plating these metals may, for example, be related to the propensity of these metals to oxidize in air, as a result of which an interfering metal-oxide or insulating layer forms on any exposed or etched surface of these metals. The interfering metal-oxide or insulating layer hinders reduction of metal ions, which is required to cause metal plating. Therefore, techniques for metal plating readily-oxidizable materials (such as tungsten, tantalum and aluminum) commonly involve a number of expensive and tedious substrate preparation steps, which are designed to avoid or prevent the formation of surface layers which can interfere with the plating processes. For example, a common technique for metal plating onto an aluminum substrate involves first zincating and then gold plating the aluminum substrate prior to plating the aluminum substrate with a metal of choice. For substrates or articles made from refractory metals such as tantalum and tungsten, the substrate preparation steps prior to metal plating often involve cumbersome high temperature processing steps.
• The interfering surface oxide layers formed on these readily-oxidizable metals also hinders etching of the surface of these metals, which may be necessary prior to any substrate preparation steps themselves. The surface oxide layer coating prevents the dissolution of the metal under conventional etching conditions. Again, a number of fairly harsh steps are required to prepare the substrate surfaces for etching. See e.g., Modern Electroplating (3rd edition), F. Lowenheim, Ed. John Wiley & Sons Inc. (1974), pp. 591-625. Further discussion of electroless plating of common materials that require multistep processing to achieve metal plating due to presence of interfering surface films may, for example, be found, in Electroless Plating: Fundamentals and Applications, Glenn O. Mallory and Juan B. Hajdu, Eds. American Electroplaters and Surface Finishers Society (1990), pp. 193-204.
• Consideration is now being given to improving metal plating systems and methods. Attention is particularly directed to simplifying techniques for metal plating of substrates on which interfering surface films form, for example, during conventional metal plating processes or steps. Further, attention is directed to substrate preparation techniques (i.e., removal of native or preformed surface oxide layers) prior to plating or etching action.
SUMMARY OF THE INVENTION
• The present invention provides systems and methods for etching and/or metal plating of substrate materials, which are usually coated with thin surface films (e.g., a native oxide film). The systems and methods may employ several in situ techniques for removing the thin surface film, including direct heating and mechanical removal. The systems and methods may alternatively exploit optical energy absorption to remove or inhibit the thin surface films before etching and/or metal plating of substrate materials. An energy beam (e.g., a laser beam), which is generated by a suitable optical source (e.g., a laser), is directed onto the surface of a substrate. Optical absorption of the directed energy beam can lead to localized heating and/or photodecomposition (also known as ablative photodecomposition) of the thin surface film.
• The removal of the thin surface film material is, in one preferred embodiment, performed “in situ” while the substrate is immersed in plating or etching solution. After the thin surface film material is removed, the plating or etching solution can act on the exposed substrate surfaces before a thin surface film can re-form or reappear. This in situ technique advantageously avoids exposure of clean substrate surfaces to air, preventing surface oxidation.
• In a variation of the in situ removal technique, the removal of the thin surface film material from the substrate surface is performed prior to immersion of the substrate in the plating/etching bath. The removal of the thin surface film material may be carried out in normal ambient or in a coating-removal enclosure having a specific inert or reducing atmosphere. The enclosure may be in close proximity or attached to the tank, which holds the bath in which the substrate is subsequently immersed for plating or etching. After removal of the thin surface film or coating, the substrate is transferred, for example, from the enclosure into the plating/etching bath, in a short time before any oxide film can reappear or regrow on the substrate surface. This variation of the removal technique advantageously avoids any significant exposure of clean substrate surfaces to air prior to plating or etching action. The transfer also may be carried out in a reducing or inert atmosphere, for example, when the enclosure is attached to the tank, to avoid all exposure to air prior to plating or etching action.
• In a further variation of the in-situ removal technique, the oxide-coated substrate is placed in contact with a suitable patterning mask. Surface oxide removal is performed through openings in the contact patterning mask to prepare designated surface pattern regions for plating or etching. A suitable patterning mask may be a photoresist pattern layer, which is applied using conventional photolithoprahic techniques (e.g., using contact or non contact photomasks). For some applications that do not require very precise feature definitions, a suitable patterning mask may, for example, be fabricated by applying masking tape (or any other non-conducting material) directly to the substrate surface to cover or mask surface regions that are not to be plated or etched.
BRIEF DESCRIPTION OF THE DRAWINGS
• Further features of the invention, its nature, and various advantages will be more apparent from the following detailed description of the preferred embodiments and the accompanying drawings, wherein like reference characters represent like elements throughout, and in which:
• FIG. 1ais a schematic illustration of an exemplary plating/etching cell arrangement, which is configured for removing an interfering insulating surface film by in situ resistive heat treatment just prior to or during the metal plating or etching of a subject substrate, in accordance with the principles of the present invention. The cell is provided with a counter electrode and pump for circulating an electrolyte or etchant.
• FIG. 1bschematically illustrates details of exemplary electrical contacts and the electrode support structures for the cell arrangement ofFIG. 1a, in accordance with the principles of the present invention.
• FIG. 2 is a schematic illustration of another exemplary plating/etching cell arrangement, which is configured for removal of an interfering insulating surface film by laser light treatment just prior to or during the metal plating or etching of a subject substrate, in accordance with the principles of the present invention. The plating/etching cell arrangement includes a moveable holder for moving the substrate relative to the laser light so that different surface portions of the substrate can be treated sequentially.
• FIG. 3 is a schematic illustration of yet another exemplary plating/etching cell arrangement, which is configured for in situ removal of an interfering insulating surface film by mechanical treatment during the metal plating or etching of a subject substrate, in accordance with the principles of the present invention. The plating/etching cell arrangement includes a scratching or scraping tool for mechanically removing the interfering insulating film from the substrate while the substrate is at least partially submerged in an electrolyte or other plating/etching fluid.
• FIG. 4 is a schematic illustration of the plating cell arrangement ofFIG. 3, which has been additionally configured to apply heat to the substrate facing away from the counter electrode, in accordance with the principles of the present invention.
• FIG. 5 is a schematic illustration of an exemplary plating/etching cell arrangement, which is configured for removal of an interfering surface film on a wire substrate by in situ mechanical stripping during metal plating or etching of the wire substrate, in accordance with the principles of the present invention. The wire substrate, which may be supplied and picked up in a reel-to-reel arrangement, is passed though a knife-edge die which strips the interfering surface film, while submerged in an electrolyte or other plating/etching fluid.
• FIG. 6 is a schematic illustration of another exemplary plating/etching cell arrangement, which is configured for in situ mechanical stripping of an interfering film on flat stock substrate during metal plating or etching of the flat stock substrate, in accordance with the principles of the present invention. The flat stock substrate is passed though a knife-edge die, which strips the interfering surface film, while the flat stock substrate is submerged in an electrolyte or other plating/etching fluid.
• FIG. 7 is a schematic illustration of a metal-plated article made from a refractory metal substrate in which the metal plating layer is bonded directly to the substrate material without any intervening substrate modification or seed layers, in accordance with the principles of the present invention.
• FIG. 8ais a schematic illustration of an exemplary plating/etching cell arrangement including a coating-removal enclosure in which inhibiting surface films are mechanically removed from substrate surfaces prior to immersion in a plating or etching bath, in accordance with the principles of the present invention. The coating-removal enclosure may be supplied with an inert or reducing gas atmosphere, and is compatible with reel-to-reel substrate supply and pick-up arrangements.
• FIG. 8bis a schematic illustration of another exemplary plating/etching cell arrangement including a coating-removal enclosure in which substrates are electrically heated in an inert or reducing ambient to remove inhibiting surface films prior to immersion in a plating or etching bath, in accordance with the principles of the present invention. Like the coating-removal enclosure ofFIG. 8a, the enclosure ofFIG. 8bis compatible with reel-to-reel substrate supply and pick-up arrangements.
• FIG. 8cis a schematic illustration of yet another exemplary plating/etching cell arrangement including a coating-removal enclosure in which a substrate is laser irradiated in an inert or reducing ambient to remove inhibiting surface films prior to immersion in a plating or etching bath, in accordance with the principles of the present invention. Like the coating-removal enclosures ofFIGS. 8aand8b, the enclosure ofFIG. 8cis compatible with reel-to-reel substrate supply and pick-up arrangements.
• FIG. 8dis a schematic illustration of an exemplary plating/etching cell arrangement in which inhibiting surface films are mechanically removed from the substrate surfaces in air prior to immersion in a plating or etching bath, in accordance with the principles of the present invention. The cell arrangement is configured with a reel-to-reel substrate supply and pick-up arrangement.
• FIG. 9 is a schematic illustration of still another exemplary plating/etching cell arrangement including a coating-removal enclosure in which a substrate may be treated to remove inhibiting surface films prior to immersion in a plating or etching bath, in accordance with the principles of the present invention. The coating removal enclosure is mounted directly above the plating/etching bath and may be configured to treat individual substrate pieces one by one, or to treat a continuous reel-to-reel supply of substrates.
• FIG. 10 is a schematic illustration of a composite substrate, which may be plated or etched in accordance with the principles of the present invention. The composite substrate has an outer material layer supported on a base substrate. The outer layer is coated with an inhibiting coating film which is removed prior to plating or etching of the composite substrate.
• FIG. 11 is a schematic illustration of an exemplary plating/etching cell arrangement, which is configured for removal of an interfering insulating surface film by induction heating or microwave irradiation just prior to metal plating or etching of a subject substrate, in accordance with the principles of the present invention.
• FIG. 12 is a schematic illustration of an exemplary induction heating arrangement, which may be used to remove inhibiting surface films on substrates with trenched surface topography such as silicon substrate wafers, in accordance with the principles of the present invention.
• FIG. 13 is a schematic illustration of another arrangement, in which an ion beam is used to remove inhibiting surface films on substrates with trenched surface topography such as silicon substrate wafers, in accordance with the principles of the present invention.
• FIG. 14 is a schematic illustration of an exemplary reel-to-reel plating/etching cell arrangement having a substrate preparation chamber in which induction heating or magnetron radiation is used for removal of interfering surface films, in accordance with the principles of the present invention.
• FIG. 15 is a schematic illustration of a stamping press, which is used to prepare shaped substrates in an oxide-layer free condition suitable for plating or etching action, in accordance with the principles of the present invention.
• FIGS. 16 and 17 are schematic illustrations of exemplary plating/etching cell arrangements in which separate tanks are provided for removal of interfering insulating surface films on a substrate and for plating the substrate, in accordance with the principles of the present invention.
• FIG. 18 is a schematic illustration of another exemplary plating/etching cell arrangement for obtaining electrolytic plating or etching of individual substrates having inhibiting surface films, in accordance with the principles of the present invention. The plating/etching cell is configured so that a high voltage pulse (or a series of pulses) is applied to the substrate to remove the interfering inhibiting surface films and then a low voltage signal, which can be a cw or a modulated cw signal, is applied to activate the desired plating and/or etching processes.
• FIG. 19 is a schematic illustration of yet another exemplary plating/etching cell arrangement for obtaining electrolytic plating or etching of long wire or flat sheet stock substrates having inhibiting surface films, in accordance with the principles of the present invention. The plating/etching cell arrangement includes a reel-to-reel material handling system. Like the plating/etching cell arrangement ofFIG. 18, the plating/etching cell is configured so that a high voltage pulse can be applied to the substrate to remove the interfering or inhibiting surface films, and then a low voltage signal can be applied to activate the desired plating and/or etching processes.
• FIGS. 20 and 21 are schematic illustrations of the alternating high voltage and low voltage pulses that can be used in electroplating or etching processes in the cell arrangements ofFIGS. 18 and 19, respectively.
• FIG. 22 is a schematic illustration of still another exemplary plating/etching cell arrangement for obtaining electrolytic plating or etching of substrates having inhibiting surface films, in accordance with the principles of the present invention. The plating/etching cell arrangement employs an electrolyte jet to co-linearly guide a high intensity laser beam for removal of the inhibiting surface films.
• FIG. 23 is a schematic illustration of a further exemplary plating/etching cell arrangement for obtaining electrolytic plating or etching of substrates having inhibiting surface films, in accordance with the principles of the present invention. The plating/etching cell arrangement uses a high intensity laser beam for removal of the inhibiting surface films for substrate surface portions under a defined volume of electrolyte.
• FIG. 24 is a schematic illustration of a sample which a contact patterning mask disposed thereon. The contact mask may be a positive or negative photo resist photo resist layer which patterned using photolithography. Plating and/or etching of the substrate occurs in the pattern openings from which inhibiting surface coatings are removed by the in-situ removal techniques of the present invention.
• FIG. 25ais a schematic illustration of the voltage pulse applied between the counter electrode and the substrate ofFIG. 24 while the latter is immersed in an electrolyte cell (FIG. 25b) in order to remove inhibiting surface coatings from the substrate surface in the pattern opening regions, in accordance with the principles of the present invention.
• FIG. 26 is a schematic illustration of the electrolyte cell ofFIG. 25bnow used to apply a small voltage for the purpose of plating or etching the substrate surface in the pattern opening regions from which inhibiting oxide layers have been removed by application of the voltage pulse ofFIG. 25a.
DETAILED DESCRIPTION OF THE INVENTION
• The present invention provides systems and methods for metal plating and etching of substrates that are covered by interfering surface films. The plating and etching methods involve in situ removal of the interfering surface films or surface preparation in such a way that plating/etching becomes possible. The in situ removal of the interfering surface films may be obtained by in situ application of heat, laser light, or mechanical abrasion, or by similar ex situ methods including, for example, placing the substrate in a reducing gas atmosphere. Accordingly, various plating/etching cell arrangements are provided for in situ application of resistive heating, laser light, mechanical abrasion, or reducing gas to the subject substrate just prior to or even as the subject substrate is undergoing etching or plating processes.
• The invention enables convenient manufacture of metal-plated articles that are made from structurally desirable substrate materials, which are readily oxidizable (e.g., aluminum, and refractory metals). For these metal-plated articles, the metal plating is deposited on or bonded directly to the underlying substrate material dispensing with the need for intermediate substrate modification or seed layers. The invention, for example, enables manufacture of metal-plated aluminum articles in which the metal coating (e.g., nickel) is deposited directly on the aluminum substrate without any intervening zinc or gold seed layers.
• It is well known that many materials, particularly metals develop an oxide coating or may have some other form of a thin surface layer, which may act as a protective coating. For those cases, it is necessary to remove the oxide or coating in some manner prior to subjecting the material to plating or etching. The removal of such surface layers is necessary for electroplating, electroless plating, immersion plating, electro etching and chemical etching of the material. The various plating/etching systems or arrangements described herein are designed to remove the protective coatings either while or just before the materials are submerged in the electrolyte, which is used for carrying out the desired plating/etching processes. These plating/etching systems or arrangements allow removal of interfering coatings or surface films on a substrate (e.g., where the coating or surface film is a naturally grown oxide) without requiring any subsequent exposure, or at least any significant subsequent exposure, of the substrate to air prior to placing it in a plating/etching cell. Some of the plating/etching systems are designed so that suitable preprocessing or coating removal steps are carried out in close proximity to the plating/etching bath, either in air or in a controlled atmosphere enclosure. Further, the plating/cell systems are designed to reduce and simplify the number of processing steps common in conventional metal plating/etching processes that are performed in separate baths, tanks or ovens, and in particular to avoid the cumbersome high temperature processing steps.
• All metallization/etching process steps can take place in situ or immediately after oxide removal so that there is no significant exposure of the substrate to air between the oxide removal and the plating/etching process steps. The inventive processes avoid conventional expensive and somewhat cumbersome coating removal steps such as are presently required in plating onto, for example, an aluminum substrate.
• Conventional procedures for metal plating aluminum substrates involve a number of steps to overcome the deleterious effects of aluminum oxide coatings that form on exposed aluminum surfaces. These steps may include zincating followed by gold plating before the metal of choice can be plated onto the aluminum substrate. By application of the present invention, interfering aluminum oxide materials can be readily removed in situ by any of the several techniques described herein, which avoid exposing the substrate material to air (or oxygen) or limit such exposure to less than a few seconds. Short exposures to air of about 1 to 10 seconds have been shown to be benign with respect to plating and etching quality. Thus, plating and etching steps may be initiated immediately or within 1-10 seconds after the interfering coating materials on the aluminum substrate are removed. This in situ processing also may be similarly advantageous for metal plating or etching of refractory metal substrates such as tungsten, tantalum, titanium, molybdenum and rhenium.
• An exemplary plating/cell arrangement or system, which is designed for in situ processing of difficult substrates (i.e., substrates whose outer surfaces are coated by an interfering film that makes direct plating or etching difficult or impossible), may include a fluid-holding tank which can hold a fluid electrolyte (e.g., copper sulfate, nickel sulfate or other chemical solutions), an electroless plating solution (e.g., electroless gold) or a chemical etchant (e.g., hydrogen fluoride, sodium hydroxide or the like). The tank may be suitably sized so that the subject substrate (which is preferably electrically conductive) can be fully submerged or partially submerged in the fluid. This exemplary plating/cell arrangement or system may be modified to include an enclosure in close proximity or attached to the fluid-holding tank. This enclosure may be used for substrate preprocessing steps including coating removal steps prior to submerging the substrate in the fluid tank.
• In one version of plating/etching cell arrangement, heat is applied to the substrate while submerged in the plating/etching solution to remove the offending film or coating from the surfaces of the substrate. The heat may be applied as resistive heat, which is locally generated by passing a high current through the substrate. The high current flow may be intermittent. A first voltage/current source, whose leads are connected to opposite ends of the substrate, is provided for this purpose. The voltage/current source may be any suitable pulser or pulsed voltage source that can produce a high current. Suitable pulsers produce pulses that are that are greater than 100 ps wide. The resistive or Joule heating due to the passage of current within the substrate serve to heat the substrate, whereby this heat can lead to dissolution or disintegration of the offending coating. The offending coating may be removed possibly by ablation, melting, or cracking due to differential thermal expansion. Once the coating has been removed and the pulser is no longer operating, the substrate may remain free of coating in the plating or etching fluid free of coating for at least about 0.1 second, but often for a much longer time on the order of minutes.
• In a variation of the inventive processes, coating removal steps, which may be similar to the heat, mechanical or other coating removal steps described above, may be performed before submerging the substrate in the fluid tank. For such processes, the plating/etching cell system or arrangement may be provided with a separate enclosure in close proximity or attached to the fluid tank. The separate enclosure may have a controlled atmosphere, which can be beneficial to the coating removal process. For example, a reducing gas (e.g., HF gas) atmosphere may be used to remove an offending substrate coating (e.g., an oxide coating) by chemical reduction of the coating. Further, for example, an inert gas atmosphere may be used to hinder oxide regrowth during heat or mechanical coating removal steps. In some instances when mechanical removal of the coating can be successfully achieved in an air ambient, the provision of a separate coating removal enclosure in the plating/etching cell arrangement may be unnecessary.
• In any of the plating/etching cell systems or arrangements including arrangements in which resistive Joule heating is utilized for removing a coating while the substrate is submerged in the fluid tank, a coating-free substrate can act as a working electrode while submerged in the fluid. A suitably positioned counter electrode may be submerged in the tank fluid for conducting electrolytic metal plating or etching. A second voltage/current source may be connected between the counter electrode and the substrate to provide current for electrolytic action. In the case where the fluid is an electrolyte, the second voltage/current source may be activated at suitable times to cause electrolytic plating or etching of the substrate when the substrate surface is free of the offending coating. Thus steady (continuous wave) or pulse plating and etching can be accomplished.
• In a typical electroplating/electroetching process using the present invention in which both the coating removal process and the plating/etching process occur within the plating bath, the second source of voltage may be applied immediately after the current pulse applied by the first voltage source (used for resistive Joule heating) is terminated. Alternatively, the second voltage/current source may be activated even before or during the application of the current pulse to remove the substrate coating. In instances where the fluid in the tank is an electrolyte, it also may be possible to obtain exchange plating (e.g., immersion plating) without the use of the second voltage source for certain electrolyte and substrate combinations. If the electrolyte fluid contains a more noble metal than the substrate material then, once the offending coating is removed from the substrate surface, the more noble metal atom will plate or deposit on the surface by replacing an exposed substrate surface atom.
• The plating/etching cell arrangement also may be used for an electroless plating (using a fluid which is an electroless plating solution). In such application, a catalyst in the electroless solution leads to plating without any applied voltage to the substrate electrode. Accordingly, it is not necessary to use the counter electrode and second voltage source to produce plating. Similarly, when a chemical etchant is used as the tank fluid, etching of the substrate may readily occur without the use of the counter electrode or second voltage source once the surface coating is removed by heat or mechanical treatment.
• In yet another version of the in situ plating/etching cell arrangement, the first voltage/current source, which is used to heat the substrate for in situ removal of the offending coating layers, may be replaced as a heat energy source by any suitable energy beam that can penetrate the fluid or the gas in the enclosure of the alternate embodiment to reach the substrate surface. The energy beam (e.g., a laser beam) may be generated by a laser. The laser beam may be directed onto the substrate surface through an optical fiber or an optical wave-guide (e.g., a light pipe). Alternatively, the laser beam may, in certain instances, be directed onto the substrate through the electrolyte without the use of a light pipe or optical fiber.
• Similar localized surface heating may occur with the use of either the voltage source or the laser beam as the heat or photoablative energy source for removing the substrate coating while the substrate is submerged or is in the preprocessing enclosure. The plating/etching cell arrangement may be configured with a suitable fluid stirring mechanism to mitigate any local boiling of the fluid or bubble formation in contact with the substrate. For example, a circulating flow system using pump may be used as a fluid stirring mechanism. The circulating flow system may be pressurized by way of the pump and use gravity flow to form a complete closed system for agitating the fluid. Alternatively or additionally, a mechanical magnetic stirrer may be placed within the fluid containing tank to maintain fluid agitation as is well known to those skilled in the art.
• In an alternate version of the plating/etching cell arrangement, a movable scraping or abrasion tool is provided to remove the offending coating by applying mechanical force to the substrate. The scraping or abrasion tool may be scanned across the substrate to remove the substrate's coating. Mechanical removal of the offending coating may be in addition or as an alternate to the heat-based removal (i.e., using the first voltage source or the energy source to remove the coating of the substrate in situ).
• An exemplary scraping or abrasion tool may be a mechanical scribe with a sharpened end, which is placed in intimate contact with the substrate surface. In operation, the scribe mechanically penetrates the coating. The mechanical scribe may be driven by a motorized moveable arm, which is preferably computer controlled. As the scribe traverses the areal dimensions of the substrate, the coating is removed from the substrate surface. Removal of the coating allows plating and etching of the substrate surface to occur immediately thereafter, while the scribe and the substrate are submerged in the plating/etching solution or, alternatively, while the scribe and substrate are positioned in the preprocessing enclosure.
• In some versions of the plating/etching cell arrangement in which the offending coating is removed within the plating/etching bath, the mechanical scribe may be used in conjunction with the first voltage source to remove a coating by application of both resistive (Joule) heating and mechanical force to the substrate surface. In such versions, the mechanical scribe may be made from conducting material, which allows localized current to flow from the scribe to the substrate. In a preferred embodiment of such a version of the plating/etching cell arrangement, the mechanical scribe is disposed to make contact with the back of the substrate (which may be sheet or flat stock). In this configuration, current that is supplied from the first voltage source flows through the substrate and heats the front of the substrate to remove the coating on the front surface of the substrate to be plated or etched (i.e. the surface facing the counter electrode).
• The in situ plating/etching cell arrangements may be configured to operate with reel-to-reel material handling systems that are commonly used in industrial processing of long lengths of wire or sheet flat stock. In these reel-to reel material handling systems, the unprocessed substrates (i.e., long length of wire or sheet flat stock) are wound on a donor reel and fed into the processing fluid (tank fluid) by a series of support wheels. Processed substrates are similarly picked up by a series of wheels and wound on a mechanically driven take-up reel. The inventive in situ plating/etching cell arrangements may be provided with suitable scrapers for mechanically removing the offending coating on the substrate surface in situ in the processing fluid or in a small preprocessing enclosure in close proximity to the fluid. For example, the substrates may be driven or pulled through a die that removes the coating by way of a sharpened inner peripheral die surface (i.e. a knife edge). The substrate feed rate may be adjusted by suitably setting the speed of the reels. The substrate feed rate for the plating/etching processes may be selected so that the wire or flat stock substrates remain submerged in the plating/etching tank fluid for at least 0.1 s, as the substrates are pulled through the die using the mechanically driven take-up reel. The shape of the die (e.g., circular or rectangular) may be designed in consideration of the shape of the substrate material (e.g., wire or flat stock).
• In some versions of the plating/etching cell arrangements, the die structures may be used in conjunction with the first source of voltage to apply heat to wire or flat stock substrates as they pass through the die. For example, opposite ends of a die may be used to pass current and to cause heating as the wire or flat stock passes through the die. This heating mechanism may be used as an alternate or an additional mechanism for removal of surface coatings. In another embodiment, heat may be generated directly in the wire or flat stock by contacting a voltage source by means of sliding contacts to the wire/flat stock directly, thereby using the resistance of the wire/flat stock in conjunction with current flow to generate the necessary heat to remove the coating.
• After removal of surface coatings using the die, a second voltage can be applied to the wire or flat stock substrate across from a counter electrode to cause electroplating or electroetching.
• Examples of plating/etching processes and cell arrangements are further described herein with reference toFIGS. 1a,1b,2-6,8a-8d,9, and11-17.
• FIG. 1ashows an exemplary plating/etching cell arrangement100 for in situ removal of interfering surface coating during plating/etching ofsubstrates103 in a plating tank orvessel101.Tank101 contains anelectrolyte102, which can be either plating or etching bath. The substrate material to be plated or etched (i.e. substrate103) is submerged inelectrolyte102.
• In general, a plating bath may be an electroless, electroplating or immersion plating or other chemical solution. For etching, the bath may be a chemical etchant such as sodium hydroxide or any other etchant known to those skilled in the art. For electroetching, the etchant may, for example, be a copper sulfate solution. Plating/etching cell arrangement100 may be provided with anoptional counter electrode104, which is used only for those applications that utilize either electroplating or electroetching. For immersion plating and electroless plating as well as for chemical etching, use of this electrode is unnecessary. Agalvanostat105 may provide the required electrolytic current for electroplating and electroetching. A simple voltage/current supply may also be used in its place. It will be understood that for electroless and immersion plating as well as for chemical etching,galvanostat105 andcounter electrode104 need not be used.
• As an initial step in the plating/etching process, a high current pulse is passed throughsubstrate103 using a first source of current/voltage (i.e. pulse generator109).Pulse generator109, which may be connected across opposite ends ofsubstrate103 bywires110 and111, supplies current pulses throughsubstrate103.Pulse generator109 may be any suitable current source capable of generating current pulses, which, for example, have spans ranging from tens of pico seconds to continuous wave (CW). The current pulses may be designed to heatsubstrate103 or its surfaces while it is immersed in102.Substrates103 or its surfaces may be heated sufficiently by the current pulses so that the interfering surface coating is removed. For electroplating and electroetching, a second source of voltage/current is provided bysource113.Source113 may be utilized prior to the heating current pulse applied bypulse generator109, concurrently, or at any time thereafter.
• A fluid circulation system may be set up to agitate the fluid contained intank101 to avoid or prevent boiling or bubbling in the fluid at the surfaces ofsubstrate103, which may be induced by localized heating caused by passage of the current pulse. The circulation system may include apump106 with aninput107 totank101, and adrain108.
• FIG. 1bshows a more detailed view an exemplary fixture assembly designed to holdsubstrate103 intank101. The fixture assembly includes a pair ofmetallic posts1001, each of which is made from twoseparate metal sections1003 and1004.Metal sections1003 and1004 may be rectangular in shape and may be held together by mechanically (e.g., bybolts1002 with1003 clamped betweensections1003 and1004).Metallic posts1001 may be fastened to a base plate (not shown) that allowsposts1001 to rest on the bottom oftank101.Pulser109 may be electrically connected tosubstrate103 by a pair of connectingwires110 and111 running along substrate support posts1001. A similar fixture assembly may be used to holdcounter electrode104 when such an electrode is used. The dimensions ofmetal sections1003 and1004 may be selected so that theirwidths1005 are small compared to the distance between them.Posts1001 may have any suitable thickness (e.g., of the order of 1-5 mm).Posts1001 may be made of material, which preferably has high electrical conductivity (e.g., copper posts for copper plating/etching). An insulating sleeve may enclose portions ofpost1001 belowsubstrate103 to avoid plating or etching ofpost1001 itself. It will be understood that the fixture assembly shown inFIG. 1bis exemplary, and that one skilled in the art can readily design alternative fixture assemblies.
• FIG. 2 shows another exemplary plating/etching cell arrangement200, in which alaser207 is exploited to irradiatesubstrate203 to be etched or plated. In plating/etching cell arrangement200,substrate203 may be at least partially submerged in an electrolyte or other plating/etching solution202 contained within atank201. Acounter electrode204 for electroplating and electroetching is also submerged insolution202 intank201. A galvanostat or other voltage/current supply205 may be connected viawires209 and210 to impose an electric potential difference betweencounter electrode204 andsubstrate203.Counter electrode204 andgalvanostat205 are not used when plating/etching cell arrangement200 is used for electroless, immersion plating or chemical etching ofsubstrate203.
• Laser207, which is disposed external totank201, may be configured so that its output light is directed into a light pipe orlight fiber206 extending intotank201.Light fiber206 may be suitably oriented so that the laser light output is incident onsubstrate203.Laser207 may be suitably pulsed to generate light pulses with pulse widths (e.g., ranging from a few ps to hundreds of microseconds). For some applications longer pulses extending to cw operation may be used. A laservoltage control unit208 may be used to set the pulse width and pulse intensity oflaser207.Laser207 may have a laser wavelength in the range of about 0.1-10 micrometers.Laser207 may, for example, be a near infrared or infrared laser emitting radiation at wavelengths that are suitable for absorption in and heating of the substrates. The intensity and duration of the laser light incident onsubstrate203 may be theoretically or empirically designed to remove coatings from the surface ofsubstrate203 by heating. The coatings/substrate may be sufficiently heated to bring about coating removal by ablation, differential expansion of the coating and the substrate leading to cracking of the coating, melting or any by other mechanism. Alternatively,laser207 may be an ultraviolet laser emitting radiation at wavelengths that are suitable for photoablative decomposition and removal of the inhibiting layer without substantial heating of the substrates.
• Substrate203 may be mounted on amoveable arm211 assembly, which may be operated by a computer (not shown) to movesubstrate203, for example, in vertical and horizontal directions. By coordinating the pulsing oflaser207 with the movement ofsubstrate203, patterned coating-removal, plating or etching ofsubstrate203 can be obtained. The degree of etching or plating ofsubstrate203 may be controlled by varying the intensity oflaser207, for example, by usingvoltage control unit208 after the coating has been removed. Additional contrast in the pattern onsubstrate203 may be achieved by makingcounter electrode204 comparable in diameter to that oflight fiber206 to limit the region of plating as a function of position ofsubstrate203. Suitable contrast in the electroplating/etching patterns onsubstrate203 also may be obtained by controlling the voltage betweencounter electrode204 andsubstrate203 asarm211 is set into motion. For this purpose,galvanostat205 may be programmed using any suitable computer or microprocessor (not shown). Laser light fromlaser207 may also be aimed directly at thesubstrate203 without the use offiber206.
• FIG. 3 shows another exemplary plating/etching cell arrangement300, in which a sharp probe or pointedscribe306 is used to remove the surface coatings onsubstrate303, while the latter is submerged in the plating/etching solution302 intank301.Solution302 may be an electrolyte or a process liquid used to cause plating or etching for cases where no external voltage need be supplied to a counter electrode. Intank301, electrolyte (or process liquid)302 at least partially coverssubstrate303. Sharp probe or pointedscribe306 may be mounted onmoveable arm307, which can be set in motion by a translation motor and computer (not shown). Sharp probe or pointedscribe306 may be spring loaded or biased so that it is in mechanical contact withsubstrate303. The contact pressures may be suitably set so that movement ofscribe306 across the surface ofsubstrate303 byarm307 results in removal of coating or oxide layers onsubstrate303.
• In plating/etching cell arrangement300, anoptional counter electrode304 is attached to a galvanostat or voltage/current supply305. For electroplating or electroetching ofsubstrate303, a voltage can be applied betweencounter electrode304 andsubstrate303 before, during, or after movingscribe306 along the surface of thesubstrate303. It will be understood that for electroless, immersion plating and chemical etching processes, galvanostat305 andcounter electrode304 are not needed or activated.
• FIG. 4 shows another plating/etching cell arrangement400, in which a sharp probe or pointedscribe410 is used to deliver an electrical current generated by a highcurrent pulser405 for passage through substrate403 (and its surface coatings), while the latter is submerged in the plating/etching solution402 in tank401. The electrical current pulses may be designed to dissipate and resistively heat the surface coatings onsubstrate403 to induce their removal.
• In plating/etching cell arrangement400, pointedscribe410 is spring loaded and may rest on either the front or back surface ofsubstrate403. In the example shown,pointed scribe410 rests on the back surface ofsubstrate403. Further, pointedscribe410 may be mounted onmoveable arm406 so that it can be moved along the surface ofsubstrate403 in a controlled manner (using, for example, a controller and computer (not shown)). Anoptional insulation material407 may cover portions ofmoveable arm406 to isolate those portions electrically or chemically. Asarm406 together with spring loadedscribe410 is moved along the back ofsubstrate403, apulser405 can deliver a pulse of current or a cw current (depending on the settings of pulser405) throughscribe410. For this purpose,current pulser405 may be connected topointed scribe410 and tosubstrate403, by connectingwires411 and412, respectively. The current transmission through the point of contact ofscribe410 on the back ofsubstrate403 results in localized heating to remove localized regions of coating on both the front and back surface of403.
• Counter electrode404, which faces the front surface ofsubstrate403, may be operated in conjunction with galvanostat orvoltage source408 at any time during the coating removal process to cause plating or etching of front surface regions ofsubstrate403. These front surface regions correspond to regions of the back ofsubstrate403 wherescribe410 has delivered current. It will be understood that for electroless, immersion plating and chemical etching,galvanostat408 andcounter electrode404 are not needed or activated.
• The plating/etching cell arrangements may be adapted for use with common industrial material handling systems (e.g., reel-to-reel systems for wire and flat stock substrates).FIG. 5 shows a plating/etching cell arrangement500, which is configured forprocessing wire substrates513. Plating/etching cell arrangement500 includes atank501 for holding electrolyte or other plating/etching chemical solutions502. A die with a sharpinner edge503 rests on adie support post505 withintank501. Coated or partially coated (e.g., oxidized)wire substrate513, which is used as raw material, is wound on adonor reel506. Fromreel506,wire513 is guided by a set ofguide wheels511 intotank501 containing processing fluids or solutions (e.g., electrolyte502).Wire513 is pulled or drawn through adie503 having knife-edges for stripping or scraping undesirable coating material from the wire substrate surface. An exemplary annular design ofdie503 is shown in the inset inFIG. 5.Exemplary die503 may have splitannular rings509, which are clamped (e.g., with one or more screws510) aroundwire substrate513.Wire substrate513, which is passed throughdie503, also may be passed through a similar hole or opening in counter electrode504 (for applications involving electroplating or electroetching) to facilitate continuous movement ofwire substrate513 throughtank501.Additional guide wheels511 may direct processedwire substrates513 out oftank501 onto a take-upreel507.Die503 may have a sharp inner circumferential portion (e.g. a knife edge514) designed to scrape the surface of passingwire substrate513 to remove any surface coatings so that unhindered plating or etching of the wire substrate material can take place. The rate at whichwire substrate513 is processed through plating/etching cell arrangement500 may depend in part on the rotation speeds ofreels506 and507. The rotation speeds ofreels506 and507 may be controlled, for example, by a computer-controlled drive motor (not shown) or by any other suitable conventional mechanical mechanisms. For electroplating and electroetching processes conducted in plating/etching cell arrangement500, a galvanostat508 (or any other suitable current/voltage source) may be connected to the die513 and acounter electrode504 using connectingwires514 and512, respectively.
• FIG. 6 shows a plating/etching cell arrangement600, which is configured for processingflat stock substrate615. Plating/etching cell arrangement600 includes atank601 for holding electrolyte or other plating/etching fluid602. A die with a sharpinner edge603 rests on adie support post605 withintank601. Coated or partially coated (oxidized)flat stock substrate615 may be fed from adonor reel605 over a set of guide rollers606 intotank601. Intank601,flat stock substrate615 is pulled or driven through a die608 with a rectangular opening.Die608 may be mounted onsupport621 disposed on the bottom oftank601.Die608 may have knife-edges or blades disposed in the rectangular opening for stripping or scraping undesirable coating material from the flat stock substrate surface. For electrolytic plating or etching processes, thecell arrangement600 may be provided with a slottedcounter electrode604 to facilitate passage of processedflat stock substrate615 throughtank601 onto take-upreel607. A galvanostat (voltage/current source)603 may be connected to die608 andcounter electrode604 bysuitable wires611 and612, respectively.
• An exemplary design ofdie608 is shown in the inset inFIG. 6.Die608 may be assembled from two splitsections609 and610 that are held together bybolts611. The dimensions of the rectangular opening indie608 may be selected so that scrapingblade620 acts against the surface offlat stock substrate615 passing through the opening and mechanically removes coating or oxide materials, which may be present on the surface.
• In some applications, die503 and die608 in plating/etching cell arrangements500 and600, respectively, may additionally or alternatively be employed as heaters to provide energy pulses for heat removal of the coating or oxides on the in-process wire or flat stock substrates. In such applications, the dies may be suitably modified and connected to a voltage/current source to deliver current pulses to the substrate, for example, in a manner similar to the one previously described with reference to plating/etching cell arrangement100 (FIG. 1a).
• FIG. 7 shows in partial cross-section the layered structure of a metal-platedarticle700, which may be fabricated using, for example, plating/arrangement600. Metal-platedarticle700 includes a flatstock substrate core710 made of readily oxidizing material (e.g., aluminum or a refractory metal). A metal platedlayer720 is disposed directly on the surfaces ofcore710, any inhibiting or interfering surface coating having been removed. Metal platedlayer720 may be any desired plating material (e.g. nickel, silver, gold, copper, cadmium, etc.).
• It will be understood that metal platedlayer720 may be formed by exchange plating from the chemical solution, which can take place after in-situ removal of inhibiting or interfering surface coatings by application of heat pulses or abrading action (FIGS. 1-7). Additional electroplating using a voltage supply or potentiostat may not be required when the usually very thin coatings obtained by exchange plating are sufficient, for example, by design of metal-platedarticle700.
• FIGS. 8a-8dand9 show plating/etching cell arrangements800 and900, in which coating removal steps are performed before the substrates are immersed in plating/etching baths801 and901, respectively. These arrangements may include controlledatmosphere enclosures803 or903 in which the coating removal steps and/or other substrate preprocessing steps may be performed. The enclosures may be in close physical proximity to the plating/etching baths (e.g.,enclosure803FIGS. 8a-8c) or mounted directly on the plating/etching baths (enclosure904,FIG. 9).FIG. 8dshows a plating/etching cell arrangement800 in which a mechanical coating removal step can be performed in ambient air just prior to immersion of the substrate in the plating/etching bath800.
• With reference toFIG. 8a, plating/cell arrangement800, which includes a plating/etching bath tank801 holding anelectrolyte8001 and a controlledatmosphere enclosure803, is configured for operation with a reel-to-reel substrate material handling system. The material handling system may include supply and pick-upreels805 and809, respectively. Raw wire orflat stock806 unwound fromsupply reel805 is passed throughenclosure803 before being processed in plating/etching bath tank801 and being rewound on pick-upreel809. The walls ofenclosure803 may be provided with slots or openings of suitable dimensions (not shown) to accommodate the passage of raw wire orflat stock806 throughenclosure803. A mechanical abrasion die804 may be located inenclosure803 to provide the necessary mechanical contact with wire orflat stock806 to remove the unwanted coating from the surfaces ofstock806, for example, by friction. The atmosphere inenclosure803 may be controlled during the coating removal processes. Inert or non-oxidizing atmospheres made of gases such as nitrogen, helium, or argon may be desirable to prevent or hinder reoxidation of cleaned substrate surfaces. The suitable specific gas or gases may be supplied from agas source802 connected toenclosure803. In operation, undesired coatings are stripped from the surface of wire orflat feed stock806 inenclosure803 bymechanical die804 so thatstock806, which passes into plating/etching bath801, has a clean surface.
• Mechanical abrasion die804 also may serve as an electrical contact to wire orflat stock806. A voltage source orpotentiostat807 connected to abrasion die804 may be used to apply an electrical voltage to wire orflat stock806 across fromcounter electrode808 to obtain electroplating or etching action as coating-free wire orflat stock806 passes throughelectrolyte8001. Processed wire orflat stock806 is drawn out ofelectrolyte8001 and wound on pick-upreel809.
• FIG. 8bshows a variation of the plating/etching cell arrangements800 in which mechanical abrasion die804 is replaced by aheating arrangement8041.Heating arrangement8041 is configured to make a pair ofelectrical contacts8042 with wire orflat stock806 as the stock passes throughenclosure803. A voltage applied across the pair ofelectrical contacts8042 byheating arrangement8041 causes an electrical current to flow through the intervening section ofstock806. The magnitude of the electrical current may be suitably selected to cause sufficient resistive or Joule heating to remove the unwanted coating/film from the surfaces ofstock806. The heating process may be conducted in an inert gas atmosphere, which is supplied fromgas tank802, to minimize surface oxidation or reoxidation.
• FIG. 8cshows another variation of plating/etching cell arrangement800 in which laser heating is employed instead of mechanical abrasion or Joule heating to remove unwanted coatings from the surface of wire orflat stock806 passing throughenclosure803. Alaser8042 may be deployed to direct light onto wire orflat stock806 passing throughenclosure803.Laser8042 may be selected to have a light wavelength suitable for absorption in and consequent heating of the stock material or absorption in the inhibiting film itself giving rise to photoablation of the inhibiting film. In operation,laser8042 may be operated at a power sufficient to heat wire orflat stock806 so that unwanted surface coatings are removed as wire orflat stock806 moves throughenclosure803. Voltage source orpotentiostat807 may be configured to make a slidingelectrical contact8044 with wire orflat stock806 as the stock passes throughenclosure803. Voltage source orpotentiostat807 may be used to apply an electrical voltage to wire orflat stock806 across from slidingcontact8044 andcounter electrode808 to obtain electro plating or etching action as coating-free wire orflat stock806 passes throughelectrolyte8001.
• In another implementation of plating/etching cell arrangement800, removal of unwanted surface coatings may be accomplished by chemical action. In such an implementation,enclosure803 may be configured to hold a reducing gas atmosphere (e.g., hydrogen) to treat the surfaces of passing wire orflat stock806 to remove unwanted coatings.
• It will be understood that inFIGS. 8a-8c,enclosure803 is shown as separated fromtank801 by an arbitrary distance, which is selected only for visual clarity in illustration. In practical implementations of plating/etching cell arrangements800,enclosure803 may be separated fromtank801 by a distance selected in consideration of the tolerable transit time of cleanedstock806 through air prior to plating or etching action. In some implementations,enclosure803 may be attached totank801 so that cleaned wire orflat stock806 can exit directly intotank801. Such implementations minimize the time cleaned wire orflat stock806 is exposed to air before submerging inelectrolyte8001.
• Conversely, for certain applications in which air exposure times are not a significant issue (e.g., the plating or etching of cleaned aluminum),enclosure803 may be completely dispensed with.FIG. 8dshows a plating/etching cell arrangement800, which is configured for processing materials such as aluminum. In this configuration, surface coatings may be adequately removed from aluminum wire orflat stock806 bymechanical die804 in air without the benefit of a controlled atmosphere ofenclosure803. It will be understood thatmechanical die804 is placed in close proximity totank801.
• FIG. 9 shows another plating/etching cell arrangement900, which is adapted for processing substrates that are not conveniently supplied by reel-to-reel material handling systems. The substrates may be discrete individual parts or parts having non-flat geometrical shapes. Plating/etching cell arrangement900 is designed so that unwanted surface coatings can be removed fromsubstrate906 having any arbitrary shape prior to etching and plating. Plating/etching cell arrangement900 includes atank901 which can hold anelectrolyte902. Anenclosure904, which has asubstrate loading door9004, is disposed directly atoptank901.Enclosure904 is provided withports903 and912 that may be used to flow gases through the enclosure. A slidingaccess door905 may be provided betweenenclosure904 andtank901.Substrate906 may be loaded throughloading door9004 and attached byfastener908 tosubstrate holding rod907, which may be adapted for controlled vertical motion to position loadedsubstrate906 in eitherenclosure904 ortank901.Rod907 is also connected to a terminal of voltage supply orpotentiostat910 by way of awire lead909.
• In preparation for plating or etching intank901,substrate906 is first suspended inenclosure901. A reducing gas (e.g., hydrogen) may be passed oversubstrate906 throughports903 and912 to chemically reduce and remove unwanted surface coatings. After removal of the unwanted surface coatings,substrate906 may be lowered through slidingdoor905 intoelectrolyte902 for plating or etching action on cleaned substrate surfaces. The intimate proximity ofenclosure904 andelectrolyte902 prevents re-oxidation ofsubstrate906 between the coating removal and initiation of plating or etching action. For plating or etching action byelectrolyte902, a potential difference may be established betweensubstrate906 and acounter electrode911 by connectingelectrode911 to the opposite polarity terminal ofsupply910.
• FIG. 10 shows an exemplarycomposite substrate1000, which may be plated or etched using the inventive systems and methods.Substrate1000 may, for example, include a silicon, orglass base1001 on whose surface afilm1002 is deposited. An inhibitingfilm1003 may reside on top offilm1002. Removal of film1003 (and/or film1002) may be necessary for successful plating or etching ofcomposite substrate1000. Such removal may be effected using the systems and methods described herein.
• The present invention also provides additional techniques and arrangements for in situ removal of inhibiting or interfering surface films to prepare substrates for plating and/or etching. These additional techniques include induction heating, microwave heating and mechanical stamping processes. The additional techniques may be individually used to prepare substrates for plating and/or etching. Alternatively, the techniques may be used in any suitable combination (e.g., abrading and stamping, stamping and microwave heating, etc.) to prepare substrates for plating and/or etching.
• Induction heating is a well known method for providing fast, consistent heat to a metallic object. Induction heating is used in many manufacturing applications, including, for example, bonding, annealing, metal working and the like. In common induction heating arrangements, an ac coil (i.e., induction coil) is placed in close proximity to a work piece or substrate. The ac coil radiates a time-varying electromagnetic field, which induces eddy currents in a surface layer (“skin depth”) of the metal or metallic work piece/substrate. These eddy currents dissipate energy in the skin depth causing the temperature of the work piece/substrate to rise. The thickness of the “skin depth” of the metal or metallic work piece/substrate depends on the frequency of the ac current driving the induction coil and on the intrinsic electric conductivity of the metal or metallic work piece/substrate. The overall work piece/substrate heating is also a function of the thermal conductivity, geometry and the immediate environment of the work piece/substrate.
• In the present invention related to metal plating and etching, substrates are subjected to induction heating to remove inhibiting surface films or regrowth. The substrates may be inductively heated when they are either (1) submerged in a plating/etching solution bath or (2) contained within an inert atmosphere in a preparation chamber in close proximity to the plating/etching bath.
• FIG. 11 shows such a preparation chamber, which may be used to prepare substrates for plating/etching. The substrates may be inductively heated in an inert atmosphere to remove inhibiting oxide or other films. Immediately after the inductive heating step, the substrates can be subjected to etching or plating action.FIG. 11 shows an arrangement in which the preparation chamber is separated from the plating/etching tank by a partition wall. Substrates that are inductively heated in the preparation chamber can be rapidly transferred to the plating/etching tank through a sliding door in the partition wall.
• The substrates may be inductively heated using either continuous wave (cw) or pulse heating in the inert atmosphere to remove inhibiting oxide or other films. The frequency of the radiated electromagnetic field produced by the induction coil at least in part determines the depth of heating of the substrate. The higher the frequency of the radiated electromagnetic field the greater is the localized surface-like nature of the heating of the substrate, due to the well known electromagnetic skin depth effects. In most instances, there is no need to heat the bulk of the substrate for simply removing the inhibiting surface films. For localized surface heating, which is most effective for removal of inhibiting surface films, it may be desirable to use induction frequencies greater than 60 kHz. A practical frequency regime is at least 100 kHz or greater. Subjecting the substrate to GHz microwave radiation, which is typically generated by a magnetron, may be especially effective in removing the inhibiting film by localizing the heating to a thin surface region. A magnetron-microwave system for removing inhibiting films is also shown inFIG. 11.
• Induction heating or microwave irradiation heating for removing surface inhibiting films may be most effective in a preparation chamber separate from the plating/etching bath in order to prevent heating of plating/etching solution itself.
• In some instances, induction heating also may be exploited to heat substrates that are submerged in a plating/etching solution. Such induction heating is likely to also heat the plating/etching solution. Circulation and/or cooling of the plating/etching solution may overcome any undesirable or excessive heating of the plating/etching solution caused by induction heating.
• FIG. 12 shows apreparation chamber1201 in which microwave or induction coil heating is used to remove a thin oxide or inhibiting film from trenches in a substrate prior to plating action. The substrate may, for example, be a semiconductor silicon substrate that has trenches built in its surface as part of common semiconductor device fabrication processes or steps.FIG. 12 shows a substrate topography with only one trench for purposes of clarity in drawing. It will be understood that the substrate may be a silicon wafer substrate, which in typical semiconductor device fabrication processes may have thousands or several thousands of such adjacent trenches in close proximity to each other. In current semiconductor device fabrication processes, it is desirable to be able to plate copper in the trenches for making electrical conductor lines. To plate copper on silicon to make electrical conductor lines, a liner (e.g., a thin film of Ta or TaN) is first deposited in the trenches onto the silicon trench surface itself or on an intermediary thin layer of silicon dioxide.
• As an alternative or in addition to the induction heating and/or magnetron heating techniques already described, ion beam heating may be used to prepare substrates for plating. The ion beam heating technique may be particularly suited for preparing “trenched” substrate topography for plating/etching.FIG. 13 shows anarrangement1300 with a movable ion gun (e.g.,ion gun1301 with lateral and rotational motion). The arrangement may be used for an ion beam process to prepare an array of trenches on a wafer surface for subsequent plating action. As shown inFIG. 13, a directed ion beam generated by the ion gun can be made to scan the wafer surface in swivel and/or raster pattern. Typically, the wavelength of ion beam is in the submicron range so that the beam can reach into the trenches in a manner that is not possible by typical wavelength laser light. The energy of the ion beam determines the effective particle wavelength. For example, for a 400 eV argon ion beam, the wavelength is on the order of 1 A. The wavelength or energy of the ion beam can be adjusted by changing the number of electron volts of acceleration voltage applied to the ion beam. The ion beam energy is adjusted so that it is sufficiently energetic to remove the inhibiting layer without affecting the liner as shown inFIG. 13.
• FIG. 14 shows the use of an induction coil (or magnetron)heating arrangement1400 in a reel-to-reel system for plating/etching continuous substrates (e.g. shim stock). In the configuration shown inFIG. 14, an induction coil or magnetron is provided in apreparation chamber1401. The raw substrate material from the stock reel passes through the preparation chamber, which may contain an inert gas or a vacuum. The passing substrate material is inductively heated inchamber1401 using either a cw or pulsed mode radiation. The substrate material then passes directly into the plating/etching bath after which it is rewound on a take-up reel. The system ofFIG. 14 is similar to the reel-to-reel systems described, for example, with reference toFIGS. 8a-8d, except for the manner in which the substrates are prepared for plating/etching. The systems ofFIGS. 8a-8duse direct current heating or the mechanical abrading of the raw substrate as it is unwound from the reel prior to entering the plating/etching bath followed by rewinding on a take-up reel. In contrast, the system ofFIG. 14 uses induction heating of the raw substrate material prior to metal plating/etching.
• Another mechanical surface film removal technique may be utilized to remove inhibiting coatings, for example, from substrates that are shaped by stamping processes. (See e.g.,FIG. 15). In such processes, astamping tool1500 is driven by force against the substrate to change the latter's mechanical form into a desired pattern or shape. The stamping processes may be operated either at room temperature or heated temperatures. When sufficient force is used to drive the stamping tool, the stamping processes not only serve their primary function of mechanically shaping the substrate, but also can result in removal of the inhibiting coating (e.g., a thin oxide layer).
• According to the present invention, a substrate stamping operation is conducted in conjunction with and in close proximity to the metal/plating operations. The stamping operation is conducted just prior to moving the resultant shaped substrate into a plating or etching bath. The shaped substrates, free of inhibiting coatings after stamping, are moved rapidly to the plating bath in a short time interval to prevent any significant re-oxidation.
• The stamping operation can be carried out in air, vacuum, or an inert gas. With suitable selection of the stamping process parameters and conditions, the stamping operation makes it possible to plate onto the re-shaped metal substrates that normally cannot be plated or are difficult to plate due to inhibiting films. New types of substrate materials can be used to substitute or replace current substrate materials for industrial applications. For example, presently copper or copper alloys are used in the connector industry for making connectors. Conventional connectors are made by stamping copper substrates or sheets and then plating them (e.g., with gold). With the present invention, it will be possible to use aluminum or titanium metal for connectors with plating occurring after stamping. The combination of stamping operations with metal/plating operations according to the present invention is particularly suited for use by the connector industry in which stamping operations are usually undertaken prior to plating.
• FIGS. 16 and 17 show other exemplary plating/etching cell arrangements, in which removal of the inhibiting oxide or film and subsequent plating operations are performed in two separate tanks. The provision of two separate tanks permits flexibility in selecting process conditions for the removal and plating processes independently.FIGS. 16 and 17 shows a reel-to-reel system6000 having twoseparate tanks6005 and6014 for oxide removal and plating, respectively.Tanks6005 and6014 may be enclosed in an optionalinert atmosphere enclosure6004. In system6000,material6002 is supplied fromreel6001 and processed material is picked up byreel6003.Material6002 passes fromsupply reel6001 by way ofsmall tracking wheels6015 into the bath of thefirst tank6005 and then intotank6014.Tank6005 may contain a bath (e.g., a acid such as sulfuric acid, or a base such as sodium hydroxide) in which the inhibiting layer onmaterial6002 is removed by application of a short electrical pulse from ahigh voltage pulser6006 to thesupply reel material6002. As seen inFIG. 16,high voltage pulser6006 has closely spacedelectrode contacts6007 which make contact withmaterial6002. The duration of the electrical pulse, which is applied acrosscontacts6007, may be about 10 nanoseconds to about 100 milliseconds. The particular voltages selected for the electrical pulse may depend on the pulse duration. Higher voltages may be required for shorter pulses. Further, a repetition rate ofpulser6006 may be determined by the speed of the reels. In order to obtain a continuous inhibiting film removal, the pulse repetition rate may be about 1-10,000 times per second.
• Alternatively or additionally, the inhibiting layer residing onmaterial6002 may be removed by means of laser heating or photoablation.FIG. 17 shows an arrangement in whichlaser6101 emits alaser beam6102 whilematerial6002 is immersed intank6005 before it is plated insecond tank6014.FIG. 17 shows setup a similar to that shown inFIG. 16 except thatpulser6006 supplying electric pulses to material6002 in first acid/base tank6005 is replaced by a pulsed orCW laser6101 positioned external totank6005.Laser6101 is positioned and operated so thatlaser beam6102 is incident on material6002 infirst tank6005. In operation for oxide or inhibiting film removal, the laser pulses may have a width in the range of 1 ns to 100 ms with a preferred value in the range of about 10 femtoseconds to 10,000 microseconds. The pulse repetition rate may be in the range of about 1-100,000 pulses per second. The laser wavelength may be in the range of about 0.1 to 10 micrometers. It will be understood that in the case wherelaser6101 is a CW laser, suitable electromechanical and/or optical scanning mechanisms may be provided to scan the laser beam with respect to the surface ofmaterial6002 undergoing plating or etching.
• The acid or base used intank6005 is preferably the same acid or base used in platingbath6011, which is contained in thesecond tank6014. The acid or base used intank6005 is free of plating metal ions. Cross-contamination or compositional change of platingbath6011 insecond tank6014 may result if fluids from the first bath adhere to material6002 upon exitingtank6005 and are transferred totank6014. To avoid such compositional change,material6002 exitingtank6005 may be wiped clean using, for example,wiper blades6013. Wiped liquids may be collected in and drained from drag-outcontainer6008. Alternate methods of cleaning or drying (e.g. radiation from a heating lamp, a nitrogen gas blower and the like) can also be employed for the same purpose.
• Plating ofmaterial6002 takes place in platingbath6011 in thesecond tank6014, either galvanostatically or potentiostatically, using galvanostat/potentiostat (or voltage source)6010.Material6002 to be plated may be biased negatively relative tovoltage source6010 using groundedcontact6009. A counter electrode/contact6012 may be biased positively directly fromvoltage source6010. Bothcontacts6009 and6012 have ends positioned insecond tank6014 containingplating bath6011 in order to contactmaterial6002. Pulse plating, which is well known to those skilled in the art, also may be used. After exitingsecond tank6014, a third tank (not shown) may be used to rinse the plated material before it is re-wound on take-up reel6003.
• It is noted thatFIG. 16 shows two power supplies—one power supply to applypulses6006 tomaterial6002 received fromsupply reel6001 while in thefirst tank6005, and a second power supply to supply required plating voltages/currents while material6002 is in second tank1014. The procedure infirst tank6005 removes the inhibitingfilm making material6002 sufficiently clean to make plating possible in thesecond tank6014.
• Additional examples of cell arrangements and plating/etching processes for substrates having inhibiting surface films are described herein with reference toFIGS. 18-23.
• FIGS. 18 and 19 show plating/etching cell arrangements1800 and1900 for individual substrates and long lengths of wire or sheet flat stock substrates, respectively. With reference toFIG. 18, incell arrangement1800,individual substrate1803 andcounter electrode1804 are mounted facing one another and immersed inelectrolyte1805. Avoltage source1806 is connected acrosscounter electrode1804 andindividual substrate1803, which serves as a working electrode. For plating or deposition processes, the negative pole ofvoltage source1806 may be connected to substrate/workingelectrode1803. Conversely, for etching processes, depending on the electrolyte used, either the positive pole or the negative pole ofvoltage source1806 may be connected to the substrate/workingelectrode1803.Voltage source1806 is configured to generate both high and low voltage pulses. In operation, a high voltage pulse (or a series of pulses) is followed by a low cw or modulated voltage signal for a period of time which is determined by the desired thickness of deposition or depth of etching.
• The high voltage and low voltage pulses are applied between substrate/workingelectrode1803 andcounter electrode1804. (SeeFIG. 18). First, ahigh voltage pulse1801, which is on the order of 20-2000V, is applied so that a current of at least about 120-200 A/cm²flows between substrate/workingelectrode1803 andcounter electrode1804.High voltage pulse1801 may have a full width at half maximum on the order of 10 ns to 1 s. These voltage and current parameters forhigh voltage pulse1801 correspond to energies of at least 5-14 Joules/cm²delivered to substrate/workingelectrode1803. Application ofhigh voltage pulse1801 results in removal of the inhibiting oxide or film on substrate/workingelectrode1803. Next, alow voltage pulse1802 on the order of 0.01-5 volts is applied between substrate/workingelectrode1803 andcounter electrode1804.Low voltage pulse1802 may have a pulse width of about 1 second, and may be modulated using suitable microprocessor or computer coupled tovoltage source1806. The application oflow voltage pulse1802 is designed to activate the desired electrolytic plating or etching processes on the surface of substrate/workingelectrode1803.
• With reference toFIG. 19,cell arrangement1900 is configured with a reel-to-reel material handling system for long length wire or sheetflat stock substrate1903. The reel-to-reel material handling system includes asupply reel1901 and a take-up reel1902 on which unprocessed and processedsubstrates1903 are respectively wound.Substrate1903, which functions as a working electrode, passes throughelectrolyte1907 facing splitcounter electrodes1904 and1905.Voltage source1908 is connected across substrate/workingelectrode1903 andcounter electrodes1904 and1905.Voltage source1908, which likevoltage source1806 is capable of generating both high and low voltage pulses, may have a low voltage terminal, a high voltage terminal and a common terminal. The high voltage and low voltage terminals ofvoltage source1908 are connected to counterelectrodes1904 and1905, respectively, while the common terminal is connected to substrate/workingelectrode1903.
• In operation,voltage source1908 generateshigh voltage pulses2001 andlow voltage pulses2002 for reel-to-reel plating ofsubstrate1903. (SeeFIG. 21).High voltage pulses2001 are applied acrosscounter electrode1904 and substrate/workingelectrode1903. A high voltage pulse2001 (or a series of pulses), likehigh voltage pulse1801, is designed to result in removal of the inhibiting oxide or film on the portion of substrate/workingelectrode1903 facingelectrode1904. Eachhigh voltage pulse2001 may only be on for the order of at most a few milliseconds.Low voltage pulses2002, which may be cw or modulated cw signals, are applied acrosscounter electrode1905 and substrate/workingelectrode1903 to portions ofsubstrate1903 that have traveled from facingelectrode1904 to facingelectrode1905.Low voltage pulses2002 may be continuous wave or modulated low voltage pulses that are designed to activate the desired plating or etching processes. With this arrangement,high voltage pulses2001 may be applied with a repetition rate of “L/v” seconds, where L is the length ofcounter electrode1904, and v is the linear travel speed at which substrate/workingelectrode1903 is pulled throughelectrolyte1907 acrosselectrode1904 andelectrode1905. The linear travel speed v may be adjusted so thatlow voltage pulses2002 are applied acrosselectrode1905 to a portion of substrate/workingelectrode1903 within less than a second after the application ofhigh voltage pulse2001 acrosselectrode1904 to the same portion of substrate/workingelectrode1903. The durations oflow voltage pulses2002 may be selected upon consideration of length ofcounter electrode1905 and the rate of deposition or etching, which rate in turn depends on the type ofelectrolyte1907 used for plating or etching and the type of substrate/workingelectrode1903. In practice, the durations oflow voltage pulses2002 may be on the order of at least several seconds, which is comparable to the time it takes for substrate/workingelectrode1903 to travel acrosselectrode1905. Additionally,low voltage pulses2002 may remain on concurrently withhigh voltage pulses2001, or alternatively may be interrupted for the durations ofhigh voltage pulses2001 that are of the order of at most a few ms.
• FIG. 22 shows another etching/plating cell arrangement2200 for etching/plating of substrates with inhibiting surface films.Cell arrangement2200 is advantageously configured for processing a three-dimensional substrate2209.Cell arrangement2200 uses anelectrolyte jet stream2208 to etch or plate the surfaces ofsubstrate2209, which is held by an electrically conductingrobotic arm2210. Avoltage supply2216 is connected acrosssubstrate2209 andelectrode2205 disposed in an electrolyte-holdingpressure cell2204.Electrode2205 serves as an anode and a cathode for plating and etching processes, respectively.Electrolyte jet stream2208 is generated from electrolyte-holdingpressure cell2204 and directed bynozzle2207 on tosubstrate2209. Further,nozzle2207 may have a diameter in the range of from 100-10,000 microns for typical applications.Electrolyte2213 is pressurized intojet stream2208 throughnozzle2207 bypump2214, which forces electrolyte2213 fromreservoir2212 intopressure cell2204.Electrolyte2213 flows intopressure cell2204 through an opening inelectrode2205, which for electroplating processes is connected to the positive polarity ofvoltage supply2216. Different portions of the surfaces ofsubstrate2209 are presented tojet stream2208 for processing by movement ofrobotic arm2210 under the control ofrobotic control system2211 andcomputer2215.
• Cell arrangement2200 further includes provisions for modifying the free-standing jet plating or etching processes with an electromagnetic energy beam (e.g., an intense laser beam) directed collinearly alongjet stream2208. For this purpose,cell arrangement2200 includes apulsed laser2210 which generates alaser beam2202.Pulsed laser2210 is aligned so thatlaser beam2202 passes throughwindow2203 intopressure cell2204 and then throughelectrode2205 alongnozzle2207. On exitingpressure cell2204,laser beam2202 is guided byjet stream2208 which acts as a wave guide or light pipe causinglaser beam pulse2202 andjet stream2208 to travel collinearly. This wave guide or light pipe arrangement permitslaser beam pulse2202 andjet stream2208 to be incident collinearly on surface portions ofsubstrate2209 presented for processing. Modification of electroplating and etching processes with an intense laser beam have been described, for example, in U.S. Pat. No. 4,497,692.
• Incell arrangement2200, apulsed laser2201 produces a set of one ormore pulses2202 of laser light for a total time on the order of 1 ps to 10 ms. The set ofpulses2202 is preferably triggered immediately after a new portion of the surfaces ofsubstrate2209 is presented tojet stream2208 for processing by movement ofrobotic arm2210. The pulsing oflaser2201 may be co-ordinated with the movement ofrobotic arm2210 bycomputer2215 which is interfaced with the roboticarm control system2211.
• In operation,laser pulses2202 incident onsubstrate2209 may be configured to have a power density on the order of 10⁵to 10¹⁰W/cm²in order to remove the inhibiting films from the surfaces ofsubstrate2209. Eachlaser pulse2202 may have a pulse width or duration on the order of about 10 ps to 10 ms, and have a fluence of 1-5,000 mJ/pulse. These parameters may be selected on consideration of the cross sectional area ofjet stream2208 as well as the thermal properties ofsample2209 and the coatings thereon.
• Whilelaser2202 is operated in a pulsed mode,jet stream2208 may be operated in a continuous mode (cw) to activate the desired plating (or etching) processes on the surface ofsample2209. The desired plating or etching can occur after the inhibiting surface films have been removed by application of the highintensity laser pulses2202.Robotic arm2210 can movesubstrate2209 so that any surface portion of2209 can be plated (or etched) as determined bycomputer2215, which synchronously controlsrobotic control system2211 and the pulsing oflaser2201. In some implementations of the invention,laser2202 may be programmed so that after emitting ahigh intensity pulse2202 that removes the inhibiting surface films, the laser emission drops to a much lower power level to induce laser-enhanced jet plating or etching as is well known in the literature.
• FIG. 23 shows anothercell arrangement2300 for modification of electroplating and etching processes with an intense laser beam.Cell arrangement2300, likecell arrangement2200, includespulsed laser2201,computer2215,voltage supply2216, and a computer controlledrobot2211 having an electrically conductingrobotic arm2210 for mountingsubstrate2209 inelectrolyte2213. However, electrolyte-holdingcell2206 andnozzle2207 ofcell arrangement2200 shown inFIG. 22 are replaced incell arrangement2300 by an insulatingflexible curtain2301, which defines avolume2303 ofelectrolyte2213.Flexible curtain2301 preferably has a conical shape.Flexible curtain2301 includes an inside electrode insert orextension2302.Electrode2302, which may be made of small strips of electrically conducting material, is disposed incurtain2301 in close proximity tosubstrate2209.Voltage supply2216 is connected acrosselectrode2302 andsubstrate2209 with a suitable polarity orientation for either electrolytic plating or etching as desired.
• In operation, different surface portions ofsubstrate2209 are moved underelectrolyte volume2303 by movement ofrobotic arm2210 under the control ofcomputer2215. Like in the operation ofcell arrangement2200, pulsedlaser2201 generates a high intensity laser pulse (or a series of pulses) to remove inhibiting surface films fromsubstrate2209. The high intensity laser pulse, which may have a duration of a few picoseconds to milliseconds, is directed inside the volume ofcurtain2301 on tosubstrate2209 to remove inhibiting surface films from surface portions ofsubstrate2209 under electrolyte volume2330. As described with reference to FIG.22, the desired plating/etching ofsubstrate2209 can occur after the inhibiting surface films have been removed by application of the high intensity laser pulse.Robotic arm2210 movessubstrate2209 so that any surface portion ofsubstrate2209 can be plated (or etched) as determined bycomputer2215, which synchronously controlsrobotic control system2211 and the pulsing oflaser2201.
• The movement ofsubstrate2209 caused byrobotic arm2210 results incurtain2301 being slid along the surface ofsubstrate2209.Curtain2301 can have small holes to allowelectrolyte2213 to recirculate throughvolume2303. Alternatively, an auxiliary pump (not shown) can be used to maintain a desired level ofelectrolyte2213 insidevolume2303 that is defined by conically shapedflexible curtain2301.
• The foregoing merely illustrates the principles of the invention. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. It will be appreciated that those skilled in the art will be able to devise numerous modifications which, although not explicitly described herein, embody the principles of the invention and are thus within the spirit and scope of the invention. For example, it will be readily understood by those skilled in the art that the removal/plating processes, which utilize two tanks with their respective baths, can also be used for individual pieces of material without the use of the reel-to-reel material handling system described with reference toFIGS. 16 and 17. In such case, a means of dipping the samples serially into the two tanks may be used instead of the reel-to-reel system.
• Further, for example, a suitable contact patterning mask may be directly disposed on the substrate surface to define surface portions for plating or etching. The contact mask may be fabricated using any convenient materials (e.g., negative or positive photoresist layers). While photoresists are one of the most common types of contact masks, other insulating materials (e.g., various tapes, varnishes, paints and lacquers) also can be used. The in situ surface coating removal techniques described herein can be used to prepare the defined surface portions for plating or etching, for example, by removing surface coating layers in the contact mask openings by application of high voltage or discharge pulses. Immediately thereafter, a second voltage pulse can be applied to provide plating or etching action in the contact mask openings in which inhibiting surface coating layers have been removed by the discharge pulse, but without affecting the contact mask pattern. The second voltage pulse used for plating/etching, which may continuous or in the form of repetitive pulse, may have an amplitude on the order of about +/−1-3V. For galvanostatic plating/etching, the second voltage pulse amplitude may be considerably higher depending, for example, on sample size. After the plating/etching step, the substrate is removed for the electrolyte solution, and the masking material stripped.
• The foregoing technique of directly masking the substrate for in situ patterned plating/etching advantageously avoids the conventional substrate patterning process steps that require oxide removal over the entire substrate surface prior to masking. The technique enables patterning to take place before the substrate is stripped of its oxide layers. The technique is particularly beneficial in applications involving substrate materials that are highly oxidizable (e.g. Al). For such substrate materials having rapid oxide growth, the substrates are conventionally patterned in an inert atmosphere. This process complexity or burden can be avoided by the foregoing technique of directly masking the substrate for in situ patterned plating/etching.
• In laboratory demonstrations, electroplated patterns of copper on stainless steel 316 substrate have been obtained by first pattern masking the substrate, then applying a voltage pulse to remove surface oxides in the mask openings followed by plating.FIG. 24 shows an exemplary substrate24-103 used in the laboratory demonstrations. An electrically insulating patterning mask24-104 is disposed on substrate24-103 so that regions24-102 are electrically insulating and therefore are not be subject to surface oxide removal and plating/etching. The exposed mask opening regions24-104 are subject to surface oxide removal and plating/etching.FIG. 25bshows a masked substrate25-201 (24-103) disposed in an electrolyte25-203 facing immersed counter electrode25-202. A power supply25-204 is configured to apply potential pulses across electrodes25-202 and25-203 immersed in the electrolyte.FIG. 25ashows an exemplary high voltage pulse25-205, which is applied to remove surface oxide layers from regions24-104. Exemplary high voltage pulse25-205 may, for example, be on the order of 20 V or greater, and have a pulse width of about 1 ms. After the surface oxide removal pulse25-205, power supply25-204 may be used to apply lower voltage pulses (e.g.,25-206) for plating or etching action on the “prepared” oxide-free surface regions24-104.
• FIG. 26 shows another view of the electrolytic cell and electrode arrangement ofFIG. 25bused of plating. For plating action, the negative polarity of supply26-204 is connected to substrate26-201 (24-103). A small voltage on the order of about 2.0 V is applied between substrate26-201 and counter electrodes26-202 for plating etching of oxide-free regions24-104. After completion of the plating process, the mask material may be conventionally removed (e.g., by stripping dissolving, ashing, etc.) leaving a pattern of plated material in regions24-104 on substrate24-201. It will be understood that the same masking technique can be used for patterned etching in regions24-104 on substrate24-201.

Claims (41)

1. A system for metal-plating and etching a substrate by action of a chemical solution in a tank containing the chemical solution, the substrate covered by an interfering surface coating, the system comprising:

a substrate-holding fixture disposed relative to the tank so that the portions of the substrate are submerged in the contained chemical solution;

a surface-coating removal mechanism that is operable “in situ” on the submerged substrate portions to remove the interfering surface coating and expose uncoated substrate surfaces to the action of the contained chemical solution,

whereby metal-plating and etching can occur directly on the substrate without interference by the surface coating.

2. The system ofclaim 1, wherein the surface-coating removal mechanism comprises a device configured for directing an energy beam onto submerged substrate surfaces to generate heat, whereby the interfering surface coating is removed.

3. The system ofclaim 1, wherein the substrate comprises electrically conductive material, and wherein the surface-coating removal mechanism comprises an arrangement for passing electrical current through the submerged substrate to generate heat, whereby the interfering surface coating is removed.

4. The system ofclaim 1, wherein the substrate-holding fixture is further configured as an electrode and a counter-electrode is disposed in the tank forming an electrolytic cell, whereby the chemical solution contained in the tank can act to electroplate or electroetch exposed clean substrate surfaces.

5. The system ofclaim 4 wherein the electrolytic cell and the surface-coating removal mechanism are configured for one of sequential operation and concurrent operation.

6. The system ofclaim 1 comprising an arrangement for circulating the chemical solution in the tank, whereby formation of bubbles on surfaces of the submerged substrate is avoided.

7. The system ofclaim 1 wherein the surface-coating removal mechanism is operable “in situ” on the submerged substrate portions to mechanically remove the interfering surface coating and expose clean substrate surfaces to the action of the chemical solution.

8. The system ofclaim 7 wherein the surface-coating removal mechanism comprises:

a movable arm; and

a scribe with a sharpened end mounted on the moveable arm, wherein the sharpened end is disposed against a surface of the substrate and wherein the movable arm is operable to scan the sharpened end along the surface of the substrate to mechanically remove the interfering surface coating.

9. The system ofclaim 7 further configured for processing wire or flat stock substrates, wherein the surface-coating removal mechanism comprises a die having a sharp edge, and wherein the system further comprises a material handling arrangement which operates to draw the wire or flat stock substrates through the die so that the sharp edge mechanically removes the interfering surface coating.

10. The system ofclaim 9 wherein the material handling arrangement comprises a reel-to-reel material handling arrangement.

11. The system ofclaim 1 wherein the surface-coating removal mechanism is disposed proximate to the tank so that the substrate can be immersed in the chemical solution while its surfaces are uncoated, whereby metal-plating and etching can occur directly on the substrate by action of the chemical solution without interference by the surface coating.

12. The system ofclaim 11 wherein the surface-coating removal mechanism comprises at least one of a mechanical abrasion device, a laser, a stamping tool, an induction heating coil, a magnetron, and an ion gun.

13. The system ofclaim 1 further comprising:

a second tank containing the chemical solution;

a substrate transferor configured to move the substrate from the first fluid holding tank to the second fluid holding tank, the transferor disposed relative to the tanks so that the uncoated substrate surfaces are exposed to the action of the contained chemical solution in the second fluid holding tank,

whereby metal-plating and etching can occur directly on the substrate without interference by the surface coating.

14. A method for metal-plating or etching a substrate by action of a chemical solution, the substrate covered by an interfering surface coating, the method comprising:

submerging portions of the substrate in the chemical solution; and

removing the interfering surface coating “in situ” while portions of the substrate are submerged in the chemical solution to expose uncoated substrate material to the action of the chemical solution,

whereby metal-plating or etching can occur directly on the substrate without interference by the surface coating.

15. The method ofclaim 14 wherein removing the interfering surface coating comprises generating heat by one of passing electrical current through the submerged substrate, directing laser light onto surfaces of the submerged substrate, and directing an energy beam onto surfaces of the submerged substrate, whereby the interfering surface coating is removed.

16. The method ofclaim 14 wherein removing the interfering surface coating comprises drawing the submerged substrates through a die with a sharp edge disposed against the surfaces of the substrate, whereby the interfering surface coating is mechanically removed.

17. The method ofclaim 14 adapted for processing wire or flat stock substrates, further comprising the step of:

operating a material handling arrangement to draw the wire or flat stock substrates through a die having a sharp edge,

wherein the surface-coating removal step comprises drawing the wire or flat stock substrates through the die so that the sharp edge contacts surfaces of the drawn substrates to mechanically remove the interfering surface coating.

18. A method ofclaim 14 further comprising:

disposing the substrate in proximity of a tank holding the chemical solution;

removing the interfering surface coating on the substrate and exposing uncoated substrate surfaces, while the substrate is proximate to the tank holding the chemical solution; and

immersing the substrate in the chemical solution while its surfaces are uncoated, whereby metal-plating and etching can occur directly on the substrate by action of the chemical solution without interference by the surface coating.

19. A method ofclaim 14 wherein removing the interfering surface coating on the substrate in a first tank and exposing uncoated substrate surfaces comprises immersing the substrate in a second tank containing a fluid that is free of plating metal ions and moving the substrate to the tank containing the chemical solution so that uncoated substrate surfaces are exposed to the action of the chemical solution,

whereby metal plating or etching can occur directly on the substrate without interference by the surface coating.

20. A metal-plated article fabricated by the method ofclaim 14, wherein the metal-plated article comprises one of a refractory metal substrate, an aluminum substrate and wherein the metal plating comprises one of cadmium, zinc, silver, gold, tin, copper, nickel and chromium.

21. The method ofclaim 14, wherein the substrate has disposed thereon a contact patterning mask defining masked and mask opening regions, wherein removing the interfering surface coating “in situ” comprises removing interfering surface coatings in the mask opening regions, whereby metal-plating or etching can occur directly on the substrate in pattern.

22. A system for plating and etching of a substrate covered with an inhibiting coating, the system comprising:

a cell for holding an electrolyte solution in which the substrate is immersed, the substrate acting as an electrode;

a counter electrode disposed in the cell; and

a voltage source connected across the electrode and counter electrode, wherein the voltage source is configured to apply a first voltage pulse having a pulse width less than about 1 second and a voltage amplitude greater than about 20V across the electrode and counter electrode, and further configured to apply a lower voltage cw signal across the electrode and counter electrode.

23. The system ofclaim 22, wherein the voltage source is configured to apply a first voltage pulse having a voltage amplitude in the range of about 20V to 1000V across the electrode and counter electrode.

24. The system ofclaim 22, wherein the voltage source is configured to apply a first voltage pulse having a pulse width in the range of about 10 ns to 100 ms across the electrode and counter electrode.

25. The system ofclaim 22, wherein the voltage source is configured to apply a lower voltage modulated cw signal across the electrode and counter electrode.

26. The system ofclaim 22, wherein the voltage source is configured to apply a lower voltage cw signal which in the range of about +0.05 to 5 volts.

27. The system ofclaim 22, wherein the voltage source is a programmable voltage source.

28. A reel-to-reel system for plating and etching substrates covered with an inhibiting coating, the system comprising:

a cell holding an electrolyte;

a supply reel for continuously feeding a substrate into the electrolyte for processing, wherein the substrate acts as a working electrode in the electrolyte;

a split set of a first and second counter electrodes mounted opposite the working electrode in the electrolyte;

a take-up reel for continuously taking up the processed substrate from the electrolyte;

a programmable voltage source connected across the working electrode and the split set of counter electrodes, wherein the voltage source is configured to apply a first voltage pulse having a pulse width less than 1 second and a voltage greater than about 20V across the working electrode and the first counter electrode, and further configured to apply a lower voltage cw signal across the working electrode and the second counter electrode.

29. The system ofclaim 28, wherein the programmable voltage source is configured to apply a first voltage pulse having a pulse width on the order of 10 ns-100 ms and an amplitude in the range of about 20-100V.

30. The system ofclaim 28, wherein the programmable voltage source is configured to apply a lower voltage cw signal having voltage amplitude in the range of about 0.01 to 10 volts between the working electrode and the second counter electrode.

31. A method for plating and etching a substrate with an inhibiting coating, the method comprising:

immersing the substrate in an electrolyte, the substrate acting as a working electrode;

disposing a counter electrode opposite the working electrode in the electrolyte;

applying a high voltage pulse between the working and counter electrodes; and

applying a low voltage pulse of the same polarity as the high voltage pulse between said working and counter electrodes following the application of said high voltage pulse.

32. A system that affords plating and etching of a substrate covered with an inhibiting coating, the system comprising:

a chamber holding an electrolyte, wherein the chamber has an optical entrance window across from and aligned with an electrolyte exit nozzle, and wherein the chamber can be pressurized to form an electrolyte jet which is incident on the substrate through the nozzle, the substrate acting as an electrode;

a counter electrode disposed in the chamber holding the electrolyte; and

a pulsed laser configured to generate a laser beam which passes through the optical window and the nozzle, and along the interior of the electrolyte jet, so that the electrolyte jet and the laser beam are both incident on to the substrate.

33. The system ofclaim 31 further comprising a voltage supply connected to said substrate and counter electrode.

34. The system ofclaim 31 further comprising a substrate holder which is movable to orient the held substrate relative to the incident electrolyte jet.

35. The system ofclaim 31 wherein the pulsed laser is configured to generate pulse widths in the range of about 10 ps to 10 ms and fluence in the range of about 1-5,000 mJ/pulse.

36. A system that affords plating and etching of a substrate covered with an inhibiting coating, the system comprising:

an electrically insulating curtain which defines a volume of electrolyte in contact with a surface portion of the substrate, the substrate acting as an working electrode; and

a counter electrode disposed in the defined volume of electrolyte;

a pulsed laser configured to generate a laser beam which passes through the defined volume of electrolyte on to the surface portion of the substrate.

37. The system ofclaim 36 further comprising a voltage supply connected to said substrate and counter electrode.

38. The system ofclaim 36 further comprising a substrate holder which is movable to orient the held substrate relative to the defined volume of the electrolyte.

39. The system ofclaim 38 wherein the pulsed laser is configured to generate pulse widths in the range of about 10 ps-10 ms and fluence in the range of about 1-5,000 mJ/pulse.

40. A method for plating and/or etching a substrate with an inhibiting coating, the method comprising:

immersing the substrate in a chamber holding an electrolyte, wherein the chamber has an optical entrance window across from and aligned with an electrolyte exit nozzle, and wherein the chamber can be pressurized to form an electrolyte jet which is incident on the substrate through the nozzle, the substrate acting as an electrode;

disposing a counter electrode in the chamber holding the electrolyte; and

pulsing a laser beam through the optical window and the nozzle and along the interior of an electrolyte jet so that the electrolyte jet and the laser beam are both incident on to a surface portion the substrate, and so that the laser beam acts on the inhibiting coating to prepare the surface portion the substrate for electrolytic plating and/or etching action by the electrolyte jet.

41. A method for plating and etching a substrate with an inhibiting coating, the method of comprising:

using an electrically insulating curtain to define a volume of electrolyte in contact with a surface portion of the substrate, the substrate acting as a working electrode;

disposing a counter electrode in the defined volume of electrolyte; and

directing a pulsed laser beam through the defined volume of electrolyte on to the surface portion of the substrate, so that the pulsed laser beam acts on the inhibiting coating to prepare the surface portion of the substrate for electrolytic plating and/or etching action by the defined volume of electrolyte in contact with the surface portion of the substrate.

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